The modern iteration of the kneeling chair came into existence in 1979. But it is being considered by more people in recent years as an acceptable sitting solution due to the epidemic of back pains caused by contemporary chairs. The central idea behind a kneeling chair is to position the body in a way that promotes active sitting (different from passive sitting caused by normal chairs) that leads to back muscles being engaged to keep the sitter upright.
The kneeling chair does this by tilting your hips forward by supporting the bottom and thighs on one pad and the knees and shins on another pad in a kneeling position. There is typically no back support in the classical kneeling chairs (although there are now some iterations with back support which specialist believe defeats the original idea behind the kneeling chair). When seated in this position an individual is forced to keep an upright position that leads to healthy spinal curvature. This sitting position also leads to reduced back pain, core muscle development, and improved posture.